We have demonstrated that mouse FcgammaRII and FcgammaRIII are not isotype specific and are capable of binding IgE immune-complexes. Furthermore, the binding of IgE immune-complexes to these receptors induces cell activation. We also have generated transfectants expressing human FcgammaRII and FcgammaRIII and we are at present studying whether our findings in the mouse system will be relevant in the human system.